A fixing device is known that includes a cylindrical heat film, a metal plate that slides on an inner peripheral surface of the heat film, a pressure roller that forms a nip portion by pinching the heat film between the pressure roller and the metal plate, a halogen heater arranged inside the heat film, and a cylindrical film guide that guides the inner peripheral surface of the heat film. With this technique, an opening is formed at a lower portion of the film guide. Both end portions of the metal plate, in a sheet conveying direction, are entirely held by the film guide to face the opening.
However, with this technique, since both the end portions of the metal plate, in the sheet conveying direction, are entirely supported by the film guide, heat of the metal plate (particularly in an image formation range) is radiated to the outside through the film guide and the heat film that slides on the film guide. The nip portion may not be efficiently heated.